package net;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

/**
 * @author krystal
 * @date 2022/11/27 18:00
 */
public class UdpEchoServer {
    DatagramSocket socket=null;

    //参数的端口表示服务器要绑定的端口
    public UdpEchoServer(int port) throws SocketException {
        socket=new DatagramSocket(port);
    }

    //通过这个方法来启动服务器
    public void start() throws IOException {
        System.out.println("服务器启动！");
        while (true){
            //循环里面处理一次请求
            //1.读取请求并解析
            DatagramPacket requestPacket=new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            //把这个DatagramPacket对象转成字符串，方便打印
            String request=new String(requestPacket.getData(),0, requestPacket.getLength());
            //2.根据请求计算响应
            String response=process(request);
            //3.把响应写回到客户端
            DatagramPacket responsePacket=new DatagramPacket(response.getBytes(),response.getBytes().length,
                    requestPacket.getSocketAddress());
            socket.send(responsePacket);
            //4.打印一个日志，记录当前情况
            System.out.printf("[%s:%d] req:%s;resp:%s\n",requestPacket.getAddress().toString(),
                    requestPacket.getPort(),request,response);
        }
    }

    //当前写的是一个回显服务器
    //响应数据就和请求时一样的
    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server=new UdpEchoServer(9090);
        server.start();
    }

}
